Load extending mechanism for material handling vehicle

ABSTRACT

A material handling vehicle including a platform, a carriage projectable and retractable with respect to the platform, at least one load support member or fork mounted on the carriage, and an elongated, telescopable extension or sheath on the load support member. An arrangement of pulley wheels and a flexible connecting member is provided to project and retract the extension with respect to the load support member, in response to the projection and retraction of the carriage. A &#39;&#39;&#39;&#39;lost motion&#39;&#39;&#39;&#39; mechanism is provided which permits a desired &#39;&#39;&#39;&#39;pretravel&#39;&#39;&#39;&#39; of the carriage before movement of the extension occurs, and this period of lost motion is repeated when the carriage is being retracted to its normal position.

United States Patent [191 Keene et al. I

[451 Mar. 4, 1975 LOAD EXTENDING MECHANISM FOR MATERIAL HANDLING VEHICLE[75] Inventors: Derek K. Keene; Louis C. Roll, both of Philadelphia, Pa.

[73] Assignee: Eaton Corporation, Cleveland, Ohio 6/l9 72 Hansen PrimaryE.\'aminerRobert J. Spar Assistant Examiner-Lawrence .l. OreskyAttorney, Agent, or FirmTeagno & Toddy [57] ABSTRACT A material handlingvehicle including a platform, a carriage projectable and retractablewith respect to the platform, at least one load support member or forkmounted on the carriage, and an elongated, telescopable extension orsheath on the load support member. An arrangement of pulley wheels and aflexible connecting member is provided to project and retract theextension with respect to the load support member, in response to theprojection and retraction of the carriage. A lost motion mechanism isprovided which permits a desired pretravel of the carriage beforemovement of the extension occurs, and this period of lost motion isrepeated when the carriage is being retracted to its normal position,

8 Claims, 9 Drawing Figures PAIENTED SHEET 1 0F 9 mmm 191s SHEET 3 0F 9Q KN. Q 5 I an \\\I, :5 L

gin. j 2m M MJ QQ .m mw 1 mm K- I wx 'snm u m 9 PATENTEU 41975 PATENTEUW 41975 SHKEI E OF 9 PATENTED MR 415175 SHEET 7 BF 9 N. QI

LOAD EXTENDING MECHANISM FOR MATERIAL HANDLING VEHICLE BACKGROUND OF THEDISCLOSURE The present invention relates to a material handling vehicle,and more particularly, to a mechanism which projects and retracts asheath or extension member with respect to a shuttle. While the presentinvention is equally applicable to any material handling or load liftingvehicle having a dual extension feature, i.e., a sheath extensible withrespect to a shuttle, while the shuttle is extensible with respect tothe carriage, the invention is especially advantageous for use with avehicle having a rotatable platform and in which the extensible portionof the shuttle includes spaced, load engaging forks, and will bedescribed in connection therewith.

In the construction and layout of modern warehouses, the trend has beentoward the use of narrower aisles in an effort to get maximumutilization out of the available floor space. Such arrangementsnecessarily limit the space available for maneuvering material handlingvehicles which must operate in the narrow aisles. This lack of space, inturn, limits the feasible size of material handling vehicles. Therefore,it has been attempted by those familiar with the art to provide amaterial handling vehicle of the type described which has a minimumpossible swing radius, consistent with the ability to handle theparticular loads.

In order to accomplish this, it may be necessary to establish twodifferent positions of the carriage at which the sheaths are fullyretracted with respect to the forks. These positions include 1. thecarriage fully retracted so that the load on the sheaths is centeredover the axis of rotation of the platform, and

2. the carriage slightly extended so that the sheath and carriagecombination is centered over the axis of rotation to permit rotation ofthe shuttle within the smallest possible radius. For most efficientoperation of this type of material handling vehicle, it is desirablethat, as the carriage moves from position (I) to position (2), thesheaths not move relative to the forks and carriage, because any suchmovement would increase the swing radius, thus necessitating an increasein the overall size of the vehicle. The distance between these positionsis referred to as the pretravel.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a material handling vehicle which is very compact,and able to maneuver in narrow aisles, even though the platform must beable to rotate with respect to the vehicle.

It is another object of the present invention to provide an improvedmaterial handling vehicle having a shuttle including extensible andretractable load supporting forks and load supporting sheaths mountedextensibly and retractably on the forks.

It is a more specific object of the present invention to provide amaterial handling vehicle of the type described wherein the sheathextends generally in response to the projection or retraction of thecarriage, but which has a selected amount of lost motion between thesheath and the forks at the beginning of the carriage projection and atthe end of the carriage retraction.

It is also an object of the present invention to provide such a materialhandling vehicle in which the lost motion device acts positively andutilizes, for its operation, the mechanism which extends the sheathrelative to the forks.

These and other objects of the present invention, which will becomeapparent upon a reading of the following detailed description, areaccomplished by the provision of an improved material handling apparatushaving a load supporting shuttle mounted for extension and retractionwith respect to a platform. A first drive means extends and retracts theshuttle. A secondary load supporting member is mounted for extension andretraction relative to the shuttle by operation of a second drive meanswhich is interconnected to the first drive means. The second drive meansincludes a lost motion connection with the secondary load supportmember. As a result, initial movement of the secondary load supportmember with respect to the shuttle lags extension of the shuttle by apredetermined travel distance.

In accordance with another aspect of the present invention there isprovided an improvement in a material handling vehicle including aplatform, a carriage projectable and retractable with respect to theplatform, at least one load support member mounted on the carriage, andan elongated, telescopable extension on the load support member, andmeans for projecting and retracting the carriage including a driveshaft. The improvement comprises:

a. a first pulley wheel mounted on the drive shaft;

b. a second pulley wheel mounted adjacent the load support member andoppositely disposed from the carriage;

c. a flexible connecting member passing around said first and secondpulley wheels, at least a portion of said member extendinglongitudinally of the extension;

d. a first drive member fixedly attached to said flexible connectingmember intermediate said first and second pulleys; and

e. driven means fixedly attached to the extension, said means defining afirst slot adapted to receive said first drive member and maintainengagement therewith, during subsequent travel of said flexibleconnecting member. Said first drive member and said slot are spacedapart sufficiently, when the carriage is retracted, to permit a selectedamount oflinear movement of said connecting member and projection of thecarriage before said first drive member engages said driven means.

In accordance with still another aspect of the present invention, thepulley wheels are sprocket wheels, the flexible connecting member is asprocket chain, and said driven means comprises a. a drive plateattached to the extension and defining said first slot, and

b. a third pulley wheel positioned adjacent said drive plate to supportsaid flexible connecting member and as said first drive member passesaround said third pulley wheel, to permit said first drive member toenter said first slot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a crosssectional plan viewof a typical material handling vehicle which may utilize the presentinvention.

FIG. 2 is a partly schematic side elevation shown partly in crosssection illustrating a portion of a shuttle incorporating the presentinvention.

FIG. 3 is a partly schematic cross-sectional view illustrating the forkextension mechanism of the invention.

FIG. 4 is a partly schematic cross-sectional view similar to FIG. 2, buton a smaller scale illustrating the carriage fully extended.

FIGS. 5 through 7 are side elevations, all on the same scale,illustrating the lost motion device of the present invention at variousstages of extension.

FIG. 8 is a rear elevation of the drive plate used herein, taken on line88 of FIG. 7, but on a scale which is twice that of FIG. 7.

FIG. 9 is a view similar to FIG. 8, and on the same scale, showing analternative embodiment of the drive plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,which are for the purpose of illustrating a preferredembodiment of thepresent invention and not for limiting the same, FIG. 1 is a plan viewof a material handling vehicle taken on a section through the masts M.The shuttle, generally designated by the numeral 10, is in its fullyretracted position which is preferred for transporting a load such asthe pallet, shown by dotted line P, because with the shuttle in theposition shown, the pallet P is centered with respect to the vehicle andthe axis of rotation of the platform 12. When the load has been removed,and it is necessary to rotate the shuttle 10, it is apparent that to doso with the shuttle in the position shown in FIG. 1 would require alarger swing diameter than the desired swing diameter shown by dottedcircle D, thereby requiring an increase in the overall size of thevehicle. Instead, the carriage 14 is projected or extended a certainpretravel distance with respect to the platform 12 to bring the entireshuttle within swing diameter D. In the subject embodiment, for example,the forks 34 are about 48 inches long and the sheaths 36 are about 40inches long; therefore, a pretravel of about 4 inches enables theshuttle to rotate entirely within diameter D, thus minimizing thevehicle size. In order for the pretravel to accomplish the statedobject, however, it is necessary that the sheaths 36 not begin to extendrelative to the forks 34 and carriage 14 during the pretravel as such anextension would increase the swing diameter undesirably. Therefore, thepresent invention is a solution to the above and other problems byproviding a lost motion connection between the drive means operating thecarriage on fork assembly and the drive means operating the sheaths, aswill be discussed below in greater detail.

The shuttle 10, as shown in FIG. 2 is still in its fully retractedposition, and shows the rotatable platform 12, and carriage 14 which isprojectable (to the right in FIG. 2) and retractable (to the left) withrespect to platform 12. A cross member 16 is fixed with respect toplatform 12 and a support bracket 18, preferably welded to cross member16, anchors one end 20 of a sprocket chain 22. The chain 22 is fixed atits other end 24 to a mounting member 26 which is rigidly attached toplatform 12. As the drive shaft 28 rotates in a counterclockwisedirection, likewise turning the drive sprocket 30 counterclockwise, thesprocket chain 22 is wound about drive sprocket 30, then around idlersprocket 32, thus moving the carriage-14 to the right in FIG. 2. Mountedon the top of carriage 14 is fork 34, and positioned in slidingengagement therewith is the sheath or extension 36. Frequently, withinone sheath there may be two spaced-apart forks instead of one fork persheath.

FIGS. 3 and 4 illustrate semi-schematically the mechanism by which thesheath 36 is extended and retracted with respect to the fork 34, inresponse to the projection and retraction of the carriage 14. The maindrive shaft 28 rotates a sprocket 38 which, in turn, drives sprocketchain 40. The chain 40 passes around a second sprocket 42 which,preferably is fixedly mounted with respect to the fork 34, and locatedat the opposite end of the fork 34 from the carriage l4. Idler sprockets44 and 46 are positioned as shown in FIGS. 3 and 4 to maintain thesprocket chain 40, passing around sprocket 42, in an orientation whereinthe portions of the sprocket chain 40 between sprockets 42 and 44 andbetween sprockets 42 and 46 extend longitudinally of fork 34 within thesheath 36. It should be noted that in FIG. 3 the carriage 14 is shown inits fully retracted position with respect to platform 12, whereas inFIG. 4, the carriage is fully projected, and in response thereto, thesheath 36 is fully extended with respect to the fork 34. Extension ofthe sheaths 36 relative to the forks 34 is effected by engagement ofdrive blocks 48,50 with the sheath, as will be described in detailbelow.

FIGS. 5, 6, and 7 illustrate a portion of the apparatus shown in FIGS. 3and 4, and in addition, the sheath drive means, generally designated bythe numeral 52. The drive means 52 generally comprises a drive plate 54attached to the rear face 56 of the sheath 36. The drive plate 54defines a central slot or passageway 55, best seen in FIG. 8 extendingperpendicular to the plane of the paper, and permitting the drive plate54 to pass over the sprocket 44 and chain 40. In addition theabove-mentioned central passageway, the drive plate defines acurvilinear slot 58 extending through the drive plate in a directionperpendicular to the plane of FIG. 5, and terminating in a terminalportion or slot 60. Offset from, but in open communication with thecurvilinear slot 58 is another slot 62. Flrst drive block or drivemember 48 and second drive member 50 are generally dumbbell-shapedassemblies. Members 48 and 50 comprise, respectively, round,-flatretaining members 64 and 64 connected to each other by means of pins 66and 66 passing through the chain 40, thus making the members 48,50immovable with respect to the chain 40.

FIG. 9 illustrates an alternative embodiment of the drive plate of thepresent invention, in which like elements are designated by the samenumbers, but with added to each. This embodiment eliminates the centralpassageway perpendicular to the plane of FIG. 7, thus making the driveplate 154 a simplified flat plate with the drive members 148,150 beingdriven in the same manner by pins 166,166 which pass through the chain140.

OPERATION Referring again to'FIGS. 5, 6, and 7, it should be noted thatFIG. 5 corresponds to FIG. 3 and FIG. 7 corresponds generally to FIG. 4,except that in FIG. 7 the sheath 36 is not yet fully telescoped orextended with respect to fork 34. In FIG. 5, with the carriage 14 fullyretracted the drive members 48,50 are located along the chain 40 withrespect to slots 60,62, respectively, by a distance which isapproximately equal to the desired pretravel of the carriage, i.e., thedistance the carriage will travel before sheath extension begins. Thisis strictly true, however, only if drive sprocket 30 and sprocket 38 arethe same size, thus making the ratio between them lzl. Therefore, as thedrive shaft 28 begins to rotate, it turns drive sprocket 30 which beginsprojecting the carriage 14 as explained previously, and sprocket 38 isalso rotated, driving the chain 40 in a direction which moves the drivemembers 48,50 upward into the curvilinear slot 58, the position shown inFIG. 5. Additional travel of the chain 40 causes drive members 48 and 50to pass partly around idler sprocket 44 to the position shown in FIG. 6,wherein the pin 66 of first drive member 48 has reached the end of slot60.

At this point, the driving force imparted to the chain 40 is conveyedthrough pin 66, acting on the bottom of slot 66, to the drive plate 54which in turn begins to move sheath 36 with respect to the fork 34. Asthe second drive member 50 passes over the 12:00 position of thesprocket 44- the pin 66' of drive member 50 enters slot 62, andmaintains engagement therewith during subsequent travel of the chain 40,such as is shown in FIG. '7. The configuration of slot 62 is such thatafter the sheath 36 has been extended fully, as shown in FIG. 4, and itis desired to retract the sheath, the pin 66 presses against the rearsurface of slot 62, and is maintained therein, during subsequentretraction of the sheath. When the sheath has been retractedapproximately to the position shown in FIG. 6, the pin 66' disengagesfrom the slot 62 as it passes over idler sprocket 44 and begins to movedownward. When this occurs, there is no longer a driving force beingtransmitted from the chain 40 to the sheath 36, and the retraction ofthe sheath is complete, even though the carriage l4 continues to retractthrough a distance which might be referred to as the post-travel whichcovers the same distance as the original pretravel.

Although the present invention is illustrated utilizing sprockets and asprocket chain, it should be clearly understood that the invention is inno way dependent upon the use thereof, and any type of pulley wheelutilizing a flexible connecting member may be utilized advantageouslyherein.

It will be apparent to one skilled in the art that the present inventionembodies apparatus for providing a selected amount of delayed or lostmotion between a first member, which is projectable and retractable inresponse to the rotation of a drive shaft and a second member, generallyprojectable and retractable in response to the projection and retractionof the first member. Furthermore, it is a feature of the subjectembodiment that the selected lost motion may occur at any desired pointduring the projection and retraction of the first and second members.

The invention has been described in great detail sufficient to enableone of ordinary skill in the art to make and use the same. Obviously,modifications and alterations of the preferred embodiments will occur toothers upon a reading and understanding of the specification and it isour intention to include all such modifications and alterations as partof our invention insofar as they come within the scope of the appendedclaims.

We claim:

I. Material handling apparatus for handling a load including a platformrotatable about a vertical axis, a

load supporting shuttle mounted on said platform for extension andretraction relative thereto, first drive means operable to extend andretract said shuttle, a secondary load supporting member mounted on saidshuttle for extention and retraction relative to said shuttle, andsecond drive means operable to extend and retract said secondary loadsupporting member, said first and second drive means beinginterconnected for simultaneous operation and said second drive meansincluding a lost motion connection with said secondary load supportingmember, whereby initial extension of said secondary load supportingmember relative to said shuttle lags extension of said shuttle by apredetermined travel distance and full retraction of said shuttle lagsfull retraction of said secondary load supporting member by apredetermined travel distance whereby said load, shuttle and secondarymember are shiftable from a fully retracted position to a position whichal lows them to rotate within a minimum swing radius.

2. Apparatus as claimed in claim 1 in which said shuttle comprises atleast one extensible and retractable fork and said secondary loadsupporting member comprises a sheath member partly surrounding saidfork.

3. In a material handling vehicle for handling a load including aplatform rotatable about a vertical axis, a carriage projectable andretractable with respect to the platform, at least one load supportmember mounted on the carriage, an elongated, telescopable extension onthe load support member, and means for projecting and retracting thecarriage including a drive shaft, the improvement comprising:

a. a first pulley wheel mounted on the drive shaft;

b. a second pulley wheel mounted adjacent the load support member andoppositely disposed from the carriage;

c. a flexible connecting member passing around said first and secondpulley wheels, at least a portion of said member extendinglongitudinally of the extension;

d. a first drive member fixedly attached to said flexible connectingmember intermediate said first and second pulleys; and

e. driven means fixedly attached to the extension, said means defining afirst slot adapted to receive said first drive member and maintainengagement therewith during subsequent travel of said flexibleconnecting member, said first drive member and said slot spaced apartsufficiently, when the carriage is retracted, to permit a selectedamount of linear movement of said connecting member and projection ofthe carriage before said first drive member engages said driven meanswhereby said load, carriage, load support member and extension areshiftable from a fully retracted position to a position which allowsthem to rotate within a minimum swing radius.

4. The improvement of claim 3 wherein said driven means comprises:

a. a drive plate attached to the extension, said plate defining saidfirst slot; and

b. a third pulley wheel positioned adjacent said drive plate to supportsaid flexible connecting member and, as said first drive member passesaround said third pulley wheel, to permit said first drive member toenter said first slot.

cent said first drive member to be received in said third slot when saidfirst drive member is received in said first slot and said second drivemember passes around said third pulley wheel.

8. The improvement ofclaim 7 wherein said third slot has a configurationwhich permits it to maintain engagement with said second drive member,while the carriage is being retracted, until said second drive memberpasses over said third pulley wheel, disengaging from said third slotand reentering said second slot.

1. Material handling apparatus for handling a load including a platform rotatable about a vertical axis, a load supporting shuttle mounted on said platform for extension and retraction relative thereto, first drive means operable to extend and retract said shuttle, a secondary load supporting member mounted on said shuttle for extention and retraction relative to said shuttle, and second drive means operable to extend and retract said secondary load supporting member, said first and second drive means being interconnected for simultaneous operation and said second drive means including a lost motion connection with said secondary load supporting member, whereby initial extension of said secondary load supporting member relative to said shuttle lags extension of said shuttle by a predetermined travel distance and full retraction of said shuttle lags full retraction of said secondary load supporting member by a predetermined travel distance whereby said load, shuttle and secondary member are shiftable from a fully retracted position to a position which allows them to rotate within a minimum swing radius.
 2. Apparatus as claimed in claim 1 in which said shuttle comprises at least one extensible and retractable fork and said secondary load supporting member comprises a sheath member partly surrounding said fork.
 3. In a material handling vehicle for handling a load including a platform rotatable about a vertical axis, a carriage projectable and retractable with respect to the platform, at least one load support member mounted on the carriage, an elongated, telescopable extension on the load support member, and means for projecting and retracting the carriage including a drive shaft, the improvement comprising: a. a first pulley wheel mounted on the drive shaft; b. a second pulley wheel mounted adjacent the load support member and oppositely disposed from the carriage; c. a flexible connecting member passing around said first and second pulley wheels, at least a portion of said member extending longitudinally of the extension; d. a first drive member fixedly attached to said flexible connecting member intermediate said first and second pulleys; and e. driven means fixedly attached to the extension, said means defining a first slot adapted to receive said first drive member and maintain engagement therewith during subsequent travel of said flexible connecting member, said first drive member and said slot spaced apart sufficiently, when the carriage is retracted, to permit a selected amount of linear movement of said connecting member and projection of the carriage before said first drive member engages said driven means whereby said load, carriage, load support member and extension are shiftable from a fully retracted position to a position which allows them to rotate within a minimum swing radius.
 4. The improvement of claim 3 wherein said driven means comprises: a. a drive plate attached to the extension, said plate defining said first slot; and b. a third pulley wheel positioned adjacent said drive plate to support said flexible connecting member and, as said first drive member passes around said third pulley wheel, to permit said first drive member to enter said first slot.
 5. The improvement of claim 4 wherein said first, second and third pulley wheels are sprocket wheels and said flexible connecting member is a sprocket chain.
 6. The improvement of claim 4 wherein said drive plate defines a curvilinear second slot, for passage therein of said drive member, said second slot being in open communication with said first slot.
 7. The improvement of claim 6 including a third slot offset from, but in open communication with, said second slot and a second drive member fixedly attached to said flexible connecting member and positioned adjacent said first drive member to be received in said third slot when said first drive member is received in said first slot and said second drive member passes around said third pulley wheel.
 8. The improvement of claim 7 wherein said third slot has a configuration which permits it to maintain engagement with said second drive member, while the carriage is being retracted, until said second drive member passes over said third pulley wheel, disengaging from said third slot and reentering said second slot. 